Utah Sen. Orrin Hatch, the longest-serving GOP senator, told CNN he is planning to run for re-election next year, abandoning his plans to quit the chamber after four decades of service.

The Utah Republican -- who promised in 2012 that his current term would be his last -- said he has changed his mind at this time, partially because he's been getting encouragement from President Donald Trump and top Republicans to run again.

Hatch, who will turn 83 later this month and has served in the upper chamber since 1977, could still change his mind again and decide to retire.

But his Thursday comments are the firmest signal yet from the veteran senator about his political ambitions.

The decision comes as Senate Majority Leader Mitch McConnell and Trump have both tried to persuade the powerful chairman of the Senate Finance Committee to run again.

"His pitch is he needs me," Hatch said of Trump. "Things are going to be just fine."

Hatch's decision comes as Trump has chosen Jon Huntsman, the former Utah governor, to be his nominee for ambassador to Russia. Some had speculated that Huntsman would have mounted a primary challenge to Hatch in 2018.

But Hatch said he spent an hour Wednesday with his "longtime friend" Huntsman and said he believed that the ex-governor was not going to challenge him.

"I don't think he would have ever run against me," Hatch said. "He didn't really want to run for Senate."

Asked if he was preparing for a tough 2018 reelection battle, Hatch said: "Anyone who wants to take me on knows it's going to be a real ordeal."